1. Application of Near-Surface Geophysics to Agricultural Drainage Pipe Detection

2. 1.In a 1985 economic survey, the Midwest U.S. was estimated to have 12.5 million hectares containing subsurface drainage systems. 2.Today, this subsurface drainage infrastructure would be worth 30 billion U.S. dollars, and the total does not include the extensive amount of drainage pipe installed since 1985. The Importance of Subsurface Drainage to Midwest U.S. Agriculture

3. Types of Drainage Pipes Clay TileCorrugated Plastic Tubing

4. Methods of Drainage Pipe Emplacement Clay TileCorrugated Plastic Tubing

5. Agricultural Drainage Pipe in the Soil Profile

6. Subsurface Drainage System Patterns

7. Farm infrastructure assessment is one reason that a better way of finding agricultural drainage pipe is needed. 1.Before modifications on pre-existing subsurface drainage systems can be attempted, the agricultural drainage pipe already in place needs to be located. 2.The methods now typically being used are time consuming, tiresome, and often result in damage to the older drainage pipe.

8. The Hypoxic Zone in the Gulf of Mexico is another reason that a better way of finding agricultural drainage pipe is needed.

9. Nitrate from agricultural subsurface drainage in the Midwest U.S. contributes significantly to the Hypoxic Zone in the Gulf of Mexico.

10. An alternative water table management approach can reduce nitrate discharge.

11. To aid in the assessment of watershed nitrate discharge, remote sensing technologies that are being tested to map agricultural subsurface drainage systems over large areas need to be verified.

12. Near-Surface Geophysical Methods Initially Tested Without Success

13. Ground penetrating radar (GPR) may provide the solution to the drainage pipe detection problem.

14. GPR Equipment Utilized in the Investigation

15. Typical GPR Drainage Pipe Detection Results Note: GPR was successful in locating, on average, 72% of the total drainage pipe present at thirteen test sites in southwest, central, and northwest Ohio. On the whole, GPR appears reasonably capable of finding clay tile and corrugated plastic tubing drainage pipe down to depths of around 1 meter.

16. Summary of GPR Results from Thirteen Test Plots in Ohio Test PlotSurface Soil Textural Class Amount of Pipe Located (%) ElectroScience Laboratorysilty clay 100 South Waterman Farm #1clay to silty clay 75 South Waterman Farm #1clay to silty clay 50 North Waterman Farm #1silty clay loam 50 North Waterman Farm #2silty clay90 Fayette County Airportclay0 Defiance County WRSIS #1clay75 Defiance County WRSIS #2silty clay100 Southeast Defiance, Ohiosandy loam100 Fulton County WRSIS #2sandy clay loam to sandy loam100 Fulton County WRSIS #1clay loam100 OSU Campus – Lima, Ohiosilty clay to silty clay loam100 OSU Ag Research Station - Hoytville, Ohioclay0

17. Items That Can Potentially Affect GPR Drainage Pipe Detection 1.Antenna Frequency 2.Computer Processing 3.Shallow Hydrologic Conditions 4.Field Measurement Equipment Parameters 5.Soil Type

18. Ohio State University ElectroScience Laboratory (ESL) Test Plot

19. Typical Field Operational Set-Up for a GPR Grid Survey

20. GPR Antenna Frequency Effects

22. Computer Processing of GPR Data

23. Impact of Shallow Hydrologic Conditions on GPR Drainage Pipe Detection

25. Field Measurement Equipment Parameter Effects

26. Impact of Soil Type on GPR Drainage Pipe Detection

27. Summary 1.GPR can be very successful in finding buried agricultural drainage pipe. 2.The best GPR data was obtained with 250 MHz antennas. 3.Computer processing is a critical component of GPR drainage pipe detection. 4.Shallow hydrologic conditions with moist soil and at least partially air-filled pipes are good for locating subsurface drainage systems. 5.Within limits, increasing the spatial sampling interval and reducing signal trace stacking still produces good quality GPR data. 6.Strong radar reflections off of layers in a sandy soil profile can interfere with the GPR drainage pipe detection response.